U.S. Pat. No. 4,105,776, issued Aug. 8, 1978 to Miguel Angel Ondetti and David W. Cushman, and its parent U.S. Pat. No. 4,046,889, issued Sept. 6, 1977, disclose certain mercaptoacyl derivatives of the naturally occurring amino acids proline and hydroxyproline. These compounds are angiotensin converting enzyme inhibitors which can be used for the reduction of blood pressure.
Ondetti et al. in U.S. Pat. No. 4,154,935 and in application Ser. No. 37,255, filed May 9, 1979, disclose certain mercaptoacyl derivatives of pipecolic acid and proline wherein the hetero ring can have one or more halogen substituents and the mercaptoacyl sidechain can have a halogen, alkyl, or trifluoromethyl substituent. These compounds are also angiotensin converting enzyme inhibitors which can be used for the reduction of blood pressure.